Prof. Pope and Mr Read, Optically active substances, etc. 475 
Optically active substances of simple molecular constitution. 
' By Professor Pope and JoHN READ, M.A. 
) | [Read 18 May 1914.] 
Notwithstanding numerous attempts, it has not hitherto been 
_ possible to prepare an optically active substance containing fewer 
than three carbon atoms in the molecule and the assumption has 
therefore been made that a considerable degree of complexity is 
necessary to enable the molecule to exist in stable enantiomor- 
| phous forms. 
After unsuccessful attempts to resolve chlorosulphoacetic acid 
and chlorobromomethanesulphonic acid the preparation and in- 
vestigation of chloroiodomethanesulphonic acid were undertaken 
with a similar object in view, and eventually the resolution of 
this substance was effected with d- and /-hydroxyhydrindamine, 
strychnine and brucine. The purest optically active ammonium 
salt of this acid yet obtained, having [M] + 43°7° in dilute 
aqueous solution, was prepared by repeated fractional precipitation 
with brucine, followed by decomposition of the brucine salt with 
ammonia; but the separation of the substance in a state of 
optical purity presents great difficulty. The above-mentioned 
salt crystallises from alcohol in colourless scales melting at 227— 
228°. The corresponding salt of the externally compensated acid 
erystallises similarly and melts at 221—222°. Barium dl-chloro- 
jodomethanesulphonate, (CHCII.SO;), Ba + 2H,0, crystallises from 
water, in which it is exceedingly soluble, in large, lustrous, colour- 
less plates. dl-Chloroiodomethanesulphonic acid is a colourless, 
hygroscopic liquid which evolves heat when mixed with water ; 
it crystallises slowly when kept in vacuo over sulphuric acid. 
It is remarkable that the optically active ammonium salt, 
which, containing only one carbon atom in the molecule corre- 
sponding to less than five per cent. of carbon, is the simplest 
optically active substance known, retains its activity with great 
persistence and cannot be caused to racemise by any of the 
ordinary agents employed for that purpose. 
